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Thoughts on raisins

Yesterday the dogs and I had a nice walk in the country - dry and intermittently sunny weather and lovely autumn colour on the trees.
When we stopped for tea I shared a few scraps of my fruit loaf with the dogs, which got me thinking about dogs and raisins. From time to time there are dire warnings about feeding raisins to dogs 'because they are toxic and cause kidney failure'. But thinking about raisins, I don't think they are toxic in the sense of poisonous for dogs - the problem surely is that they act like a diuretic, soaking up fluid from the body so that the kidneys can't function properly. Raisins are the largest of the dried fruits used in cooking (especially cake-making), so most people have them in their cupboards. They are dried - but rehydrate easily when they come into prolonged contact with fluid, drawing fluid into themselves. So if dogs eat them in some quantity, they are going to collect fluid from the body on their journey to the stomach, which may lower the fluid in the body to a dangerous level that causes the kidneys to stop functioning. Presumably pre-soaked raisins would not have the same effect, because they wouldn't be able to absorb any more fluid from the body. So cooked raisins - for example, in my fruit loaf - shouldn't be dangerous because they have already absorbed water from the dough or cake mixture. And the odd one or two dried raisins shouldn't be a problem - all my Cavaliers have loved them as occasional treats and had no ill effects. The reported cases have always eaten a lot of raisins in one go.

Birds have a similar problem with bread - you should always pre-soak dry bread that you put out for the birds, as dry bread sitting in their stomachs absorbs too much body fluid, as well as causing acute discomfort as it swells in a tiny tummy.

Have no idea if these thoughts have any medical validity - they just kept me nicely occupied sitting in the sun yesterday!

Yesterday the dogs and I had a nice walk in the country - dry and intermittently sunny weather and lovely autumn colour on the trees.
When we stopped for tea I shared a few scraps of my fruit loaf with the dogs, which got me thinking about dogs and raisins. From time to time there are dire warnings about feeding raisins to dogs 'because they are toxic and cause kidney failure'. But thinking about raisins, I don't think they are toxic in the sense of poisonous for dogs - the problem surely is that they act like a diuretic, soaking up fluid from the body so that the kidneys can't function properly. Raisins are the largest of the dried fruits used in cooking (especially cake-making), so most people have them in their cupboards. They are dried - but rehydrate easily when they come into prolonged contact with fluid, drawing fluid into themselves. So if dogs eat them in some quantity, they are going to collect fluid from the body on their journey to the stomach, which may lower the fluid in the body to a dangerous level that causes the kidneys to stop functioning. Presumably pre-soaked raisins would not have the same effect, because they wouldn't be able to absorb any more fluid from the body. So cooked raisins - for example, in my fruit loaf - shouldn't be dangerous because they have already absorbed water from the dough or cake mixture. And the odd one or two dried raisins shouldn't be a problem - all my Cavaliers have loved them as occasional treats and had no ill effects. The reported cases have always eaten a lot of raisins in one go.

Birds have a similar problem with bread - you should always pre-soak dry bread that you put out for the birds, as dry bread sitting in their stomachs absorbs too much body fluid, as well as causing acute discomfort as it swells in a tiny tummy.

Have no idea if these thoughts have any medical validity - they just kept me nicely occupied sitting in the sun yesterday!

Kate, Oliver and Aled

Kate; i have understood that it is grapes thay are bad for dogs and toxic? How does one explain that grapes are toxic?

Interesting in the link Blondiemonster gave (a) that it says nobody actually knows the cause and (b) that it doesn't list as a possible cause the diuretic effect of raisins. I also wonder if grapes and raisins are different - yes I know raisins are dried grapes, but, for example, I can cheerfully eat the small dried seeds in raisins but gag on the sour fresh seeds in grapes. I wonder if seedless grapes are also toxic? If it is the seeds in grapes that cause the problem that might account for why the dog has to eat a huge amount of grapes before it causes harm. It's also interesting that all the cases I have read about have been large, deep-chested dogs (I can remember a labrador, a German shepherd, a viszla or weimeraner) who are also prone to bloat. Though this might simply be that larger breeds are better able to steal off tables and get into cupboards!

Raisins are clearly not toxic for all dogs (my B&T ate quite a lot in a day, but not all at once), at least not in small quantities - it seems to be quantity and breed that counts. Breeds do differ - there's one kind of wormer that is lethal for any variety of collie but OK for other breeds.

I'm not sure what active ingredient in grapes / sultanas / raisins /currants etc is, but they wont kill a dog on one occasion of them eating some. I had read (and I cant find the link at the moment - I'll keep looking) that it is a cumulutive effect, so over time the kidneys get damaged. Not something I would want to risk to be honest..................

They can kill a dog in a single instance of eating them --there is a case of as few as 7 raisins killing a labrador. It is believed they may also have a cumulative effect. The cause isn't understood at all but seems to be some chemical in grapes that also would be in raisins. Not worth the risk IMHO if a dog gets into them -- I rushed Leo to the vet last summer when he ate a lot of raisins in a brack (bread) he got hold of off a table. .

The UK vet paper is especially good -- read that a while back. It notes that a dachshund weighing about what a cavalier would weigh died of renal failure after eating only 4-5 grapes so this can be a very serious issue and never one to underestimate.